Gaseous discharge electrode assembly and tube



March 10, 1953 s. H. STA-VRO GASEOUS DISCHARGE ELECTRODE ASSEMBLY AND TUBE Filed Dec. 29, 1951 INVENTOR. STEPHEN H. 5 TA VRO ATTORN EY Patented Mar. 10, 1953 1 GASEOUS DISCHARGEELE'GTRODE ASSEMBLY AND? TUBE Stephen H. Stavro, West Roxbury,Mass., assignor:

to Sylvania. Electric Products. Inc.; a corporation of Massachusetts Application December 29, 1951, Serial No. 264,045

4 Claims. .1

The presentinvention. is concerned" witlrimprovements inthe construction of gaseous: dis.- charge tubes of the type used in waveguide systems-for switching and for attenuation.

Attenuators, duplexers, as. well as combined attenuators and duplexers, rely .on an ionized gaseous discharge 'to change the condition of" a wave guide system during the discharge. The initial condition of the Wave guide is restored after such discharges. Duplexers include both transmit-receive (TR) and anti-transmit-receive (A'I'R) types of tubes.

Operation of a TR tube in a wave' guide system may be considered as an example. When the wave guide system is quiescent or carrying low level energy the tube should not be ionized, in sharp contrastto its condition of intense ionization in the presence of highxlevel energyzintthe wave guide system. Th discharge'resultsfrom.

electrode for maintaining constantly available limited volume of weakly ionized gas which promotes almost instantaneous discharge at the gap electrode upon incidence of each high-level burst; and this discharge spreads rapidly through the tube.

Assembly of the keep-alive in the tube is ordinarily very critical. This factor tends to limit the manufacturing yield of good tubes, andto limit tube life. An object of the present invention is to provide an improved assembly of electrode in such tubes, including keep-alive and discharge-gap electrodes, which will not upset the electrical performance of the tube, yet which can be more readily assembled. A further object is to provide a tube including such novel assembly of electrodes having longer life.

The keep-alive electrode is usually contained within a hollow conical gap electrode. The end of the keep-alive electrode is critically close to the open end of the hollow conical electrode. The conical form of gap electrode provides appropriate capacitance in producing resonance at the discharge gap, and this form has been used for many years.

The hollow conical gap electrode, in the illustrative application of the invention, is modified by providing an annular bulge about the end of the keep-alive electrode. The mechanical assembly problem of insuring separation between the keep-alive electrode and the inside wall of 2 thehollow gap electrode; is vastly simplified; and the life ofthe tube-is also vastly increased by this bulge. as will beseen,- without materially-changing the capacitance of the-gap'electrodes.

The nature of the invention and further features ofnovelty will be" better appreciated the following detailed description ofillustrative embodiment thereof. In the accompanying drawings:

Fig. l is the longitudinal cross section of an illustrative embodiment of the'TR tube embodying features of the present invention;

Fig. 2 is a transverse cross'sectional view-along the line 2-2' in Fig. 1; e

Fig; 3 is agreatly enlargedcross sectional' View of portion of Fig; 2 and Fig. 4 is a'view similar to Fig. 3 'of'ftheprior construction. 7 The IR tubein Fig. l is; seen to" havea length of rectangularmetallic; wave guide Hlunited to metal end flanges l2- and i4 and these flanges have glass window 16 and lB-for transmission of microwave energy through waveguide, Hi. The waveguide is filled with an ionizing. and quenching gas mixture typically argon and. water vapor at" a total pressure of 10 mm. 'Hg. Whenhigh level energy is incident upon one of the Windows it is desired that an ionized discharge should occur and spread through the tube to cause reflection of the energy with a minimum of transmission. Paired gap electrodes are provided, including one pair 20, 22 and a second pair 24, 26, both being hermetically sealed to waveguide body [0. As seen in Fig. 2, electrode 26 is of special construction, including keep-alive electrode 28 supported by a glass button 30 and having a glass sheath or bead 32 extending to a point flush or slightly beyond the tip 28a of keep-alive electrode 28 (Fig. 3). Glass button 30 is sealed to metal ring 34 that is hermetically sealed to ring 36, in turn sealed to waveguide body It. Concentrically about keep-alive electrode 28 is a hollow conical gap electrode 38. It will be seen that gap electrodes 24 and 26 represent a capacitance between opposite walls of guide ID, in addition to their function as discharge gap electrodes, that resonates with inductive vanes 21 disposed laterally of the discharge gap 24, 26. A similar pair of vanes is provided adjacent gap electrode 22.

In Fig. 3 there is seen a conical electrode 38 having an open-tipped conical portion 38a joined to a shoulder 38b and to a cylindrical portion 380. Shoulder 38b and cylindrical portion 380 constitute a bulge surrounding tip 280.. The tip of the keep-alive is spaced further away from the inside wall of hollow conical electrode 38 than in the usual tube construction (Fig. 4) where the conica'l electrode 38' is formed as a cone. The beaded tip 28a of the keep-alive is spaced a distance S from the nearest part of shoulder 38b, and a substantially equal distance S radially from the end 28a to the lateral wall 380 of the bulge, in contrast to the much smaller spacing S in Fig. 3.

In operation, a high voltage, of the order of 800 volts, is impressed between keep-alive electrode 28 and the hollow gap electrode 38. This produces weak ionization of the gas volume within electrode 38 between the end 2811 of the keepalive and the open end of conical portion 38a. The gas ions speed the response to high-level energy bursts, and a rapidly spreading discharge in the tube results. The spacing between the open end of portion 380. and the end 28a of the keep-alive is usually very small, only .040 inch in an illustrative embodiment, using both forms of electrodes shown in Figs. 3 and 4. During operation metal sputters from the keep-alive, spreading over the end of sheath 32 and on the inside wall of electrode 38. With the conventional construction in Fig. 4, the sputter prematurely reduces the spacing between sputter-coated glass 32 and gap electrode 38.

The increase in spacing represented at S and S in Fig. 3 makes initial assembly of the electrodes far simpler, an operation that at best is difilcult because of the small separation involved and because of the difficulty of inspecting the relative positions of these electrodes during assembly operations. It has been found that resonance at gap 24, 26 can still be effectively achieved by seizing gap electrode 24 and forcing it into proper spacing from gap electrode 26, and further that the voltage needed between the keep-alive and the hollow gap electrode for effecting the desired stand-by weak ionization is not appreciably increased. Thus, desirable electrical performance characteristics are preserved, yet less critical construction is involved and longer tube life is realized, with the modification involved.

What is claimed is:

1. A gaseous discharge device having a discharge gap structure including an open-tipped hollow generally conical gap electrode and a keep-alive electrode within said gap electrode having one end therein, said hollow gap electrode embodying an annular bulged portion about said end of said keep-alive electrode.

2. A gaseous discharge device having a resonant discharge gap structure including an opentipped hollow generally conical gap electrode and a laterally glass-sheathed and bare-ended keep-alive electrode within said gap electrode having one end therein, said hollow gap electrode embodying an annular bulged portion about said end of said keep-alive electrode.

3. A gaseous discharge device having a discharge gap structure including an open-tipped hollowgenerally conical gap electrode and a keep-alive electrode within said gap electrode having one end therein, said hollow gap electrode embodying an annular bulge-d portion about said end of said keep-alive electrode, the end of said keep-alive electrode having approximately equal spacing radially and axially from the inside surface of said bulged portion.

4. An electrode assembly for a gaseous discharge device including generally conical hollow electrode having an open tip, and an ionizing electrode within said hollow electrode having an end spaced inward a critically short distance from said open tip, said hollow electrode embodying an annular outwardly bulged portion surrounding said end of the ionizing electrode.

STEPHEN H. STAVRO.

REFERENCES CITED The following references are of record in the file of this patent: 

